Solving Camera Lens Problem for Film Size of 24x36mm

[gadawg90]

The actual frame size of "35-mm" film is 24 mm x 36 mm. You want to take a photograph of your friend, who is 1.70 m tall. Your camera has a 60.0 mm focal length lens. How far from the camera should your friend stand in order to produce a 36.0 mm-tall image on the film?



i thought you would use the equation hi=-(f/do-f)ho




I did this and i got 22.4 cm. which is wrong. please help I am stuck

 

[rl.bhat]

Your formula is correct.
Convert all lengths to meter and find do.